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Changing Earth’s Climate

Changing Earth’s Climate. `The balance of evidence suggests that there is a discernible human influence on global climate '. Intergovernmental Panel on Climate Change (United Nations), Second Assessment Report, 1996.

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Changing Earth’s Climate

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  1. Changing Earth’s Climate

  2. `The balance of evidence suggests that there is a discernible human influence on global climate ' Intergovernmental Panel on Climate Change (United Nations), Second Assessment Report, 1996

  3. `There is new and stronger evidence that most of the warming observed overthe last 50 years is attributable to human activity' Intergovernmental Panel on Climate Change (United Nations), Third Assessment Report, 2001

  4. `Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in greenhouse gas concentrations.' Intergovernmental Panel on Climate Change (United Nations), Fourth Assessment Report, 2007

  5. `Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.' Intergovernmental Panel on Climate Change (United Nations), Fourth Assessment Report, 2007

  6. Greenhouse Gasses • Sunlight heats up Earth’s surface • Earth radiates heat back into the air • Greenhouse gasses absorb this heat and don’t let Earth’s heat out

  7. Increased Greenhouse Gases Earth’s “cooling” system is “clogged”

  8. Evidence from the Earth

  9. Observations of recent climate change Global mean temperature Global average sea level Northern hemisphere snow cover

  10. Global Instrumental Temperature Record 10 warmest years

  11. 2007 390 Carbon Dioxide Concentration 380 370 360 Carbon Dioxide Concentration (ppmv) 350 340 330 320 310 1960 1970 1980 1990 2000

  12. Reconstructing past climates How we get data from the past • Deep ocean cores • Tree rings • Historical documents • Coral cores • Ice cores

  13. Reconstructed Surface Temperatures

  14. Past CO2 concentrations 380 370 360 350 Mauna Loa, Hawaii (1958 - present) 340 330 Siple Station (1750 - ) Carbon Dioxide Concentration (ppmv) 320 310 300 290 280 270 1750 1800 1850 1900 1950 2000

  15. Present CO2 concentration (383 ppmv) CO2 concentration after 50 years of unrestricted fossil fuel burning (600 ppmv) 300 270 240 CO2 (ppmv) 210 180 Temp. Proxy 800 600 400 200 0 Thousands of Years Before Present Petit et al., 1999; Siegenthaler et al., 2005; EPICA Community members, 2004

  16. Signs that global warming is underway • Sea level rising • by thermal expansion AND ice melt • Sea ice melting (Arctic and Antarctic) • Glaciers melting worldwide • Arctic and Antarctic Peninsula heating up fastest • Melting on ice sheets is accelerating • More severe weather (droughts, floods, storms, heat waves, hard freezes, etc.) • Bottom line: • These changes do not fit the natural patterns unless we add the effects of increased Greenhouse gasses

  17. Some climate change facts • Earth is 1°F warmer than 100 years ago • Not equally distributed • Some areas have warmed 11°F • Weather becoming more variable and more severe

  18. Scientists have no doubt

  19. Glaciers fluctuate with climate 18,000 years ago Present Glacier ice Sea ice

  20. Predicted changes of human climate change • For over 30 years, scientists have predicted increased greenhouse gasses will cause unnatural changes • By 2000 we have seen: • Antarctic sea ice break-ups • Antarctic Peninsula warming • Arctic sea ice melting • Faster Arctic warming (11°F!) • Melting of small glaciers and ice caps • Sea level rise

  21. Antarctic Sea Ice Break-ups

  22. Antarctic Sea Ice Melting

  23. Arctic Sea Ice Melting

  24. Arctic sea ice extent 0.4 0.2 0.0 Ice Extent Anomaly (106 km2) -0.2 -0.4 -0.6 -0.8 1980 1985 1990 1995 2000 2005

  25. Melting of small glaciers and ice caps 2004 1941

  26. Carroll Glacier 1906 2004

  27. McCarty Glacier, Alaska

  28. Muir and Riggs Glaciers

  29. 1993 2000

  30. Kilimanjaro 1970 2005

  31. Qori Kalis 1978 2002

  32. Patagonia 1928 2004

  33. Who cares about glaciers? • ~80% of world’s water supply • Rapidly retreating worldwide • Glaciers and ice caps gone by 2100 or sooner • Major ice sheets also retreating 2004 1941

  34. Sea-level rising • Thermal expansion (warmer water expands and needs more space) • Addition of water from melting ice • Melting ice sheets • Greenland: 7.4 m (25’) potential • Antarctica: 74 m (250’) potential

  35. Greenland satellite melt record 1992 2005

  36. This is how much ice melted in just one year. 1 year of melt! R. Huff, J. Box, S. Starkweather, T. Albert

  37. Sea Level Rise • Areas in red will be under water if all Greenland melts.

  38. Earth if Antarctica melts

  39. Sea-level rise

  40. Additional consequences • Fastest extinction rate of life on Earth in 65 Million years (1000x normal rate) • Increased disease (e.g. asthma, malaria) • Increased poverty and hunger • Sea level rise • More extreme weather • Droughts • Flooding • Heat-waves • Storms

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